operator==,!=,<,<=,>,>=,<=>(std::filesystem::path)

`friend bool operator==( const path& lhs, const path& rhs ) noexcept;`	(1)	(since C++17)
`friend bool operator!=( const path& lhs, const path& rhs ) noexcept;`	(2)	(since C++17) (until C++20)
`friend bool operator<( const path& lhs, const path& rhs ) noexcept;`	(3)	(since C++17) (until C++20)
`friend bool operator<=( const path& lhs, const path& rhs ) noexcept;`	(4)	(since C++17) (until C++20)
`friend bool operator>( const path& lhs, const path& rhs ) noexcept;`	(5)	(since C++17) (until C++20)
`friend bool operator>=( const path& lhs, const path& rhs ) noexcept;`	(6)	(since C++17) (until C++20)
`friend std::strong_ordering operator<=>( const path& lhs, const path& rhs ) noexcept;`	(7)	(since C++20)

Compares two paths lexicographically.

1) Checks whether lhs and rhs are equal. Equivalent to !(lhs < rhs) && !(rhs < lhs).

2) Checks whether lhs and rhs are not equal. Equivalent to !(lhs == rhs).

3) Checks whether lhs is less than rhs. Equivalent to lhs.compare(rhs) < 0.

4) Checks whether lhs is less than or equal to rhs. Equivalent to !(rhs < lhs).

5) Checks whether lhs is greater than rhs. Equivalent to rhs < lhs.

6) Checks whether lhs is greater than or equal to rhs. Equivalent to !(lhs < rhs).

7) Obtains the three-way comparison result of lhs and rhs. Equivalent to lhs.compare(rhs) <=> 0.

These functions are not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when std::filesystem::path is an associated class of the arguments. This prevents undesirable conversions in the presence of a using namespace std::filesystem; using-directive.

The <, <=, >, >=, and != operators are synthesized from operator<=> and operator== respectively.

(since C++20)

Parameters

lhs, rhs

the paths to compare

Return value

1-6) true if the corresponding comparison yields, false otherwise.

7) std::strong_ordering::less if lhs is less than rhs, otherwise std::strong_ordering::greater if rhs is less than lhs, otherwise std::strong_ordering::equal.

Notes

Path equality and equivalence have different semantics.

In the case of equality, as determined by operator==, only lexical representations are compared. Therefore, path("a") == path("b") is never true.

In the case of equivalence, as determined by std::filesystem::equivalent(), it is checked whether two paths resolve to the same file system object. Thus equivalent("a", "b") will return true if the paths resolve to the same file.

Example

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 3065	C++17	allowed comparison of everything convertible to `path` in the presence of a using-directive	made hidden friend

compare	compares the lexical representations of two paths lexicographically (public member function)
equivalent (C++17)	checks whether two paths refer to the same file system object (function)

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